The uses for LEDs have grown. In particular, there is increase interest in the employment of LEDs as light sources for projection engines/system. This growth has been due in large part to the increase in the light output of the LEDs. Historically, the low light output from LEDs made them impractical for use in applications requiring significant light output, for example, in outdoor applications. However, as LED light output continues to increase, LEDs are finding application in an increase number of areas.
The apparent light output of an LED depends on a number of factors. Such factors include the viewing angle of the LED with respect to the optical center as well as the brightness of the LED. The brightness of the LED is itself a function of a number of factors. For example, the brightness can be affected by the amount of current being delivered to an LED and the junction temperature of the LED.